The present invention relates to a cigarette-making machine with an auxilliary tobacco supply unit.
Cigarette-making machines including an input chamber from which shredded tobacco is withdrawn by the operation of a carding unit, to be supplied to a descending chimney, are known. At the lower end of this latter there is disposed a feed conveyor which conveys tobacco towards the lower end of an ascending output chimney.
In general the said descending chimney serves as an accumulation magazine in that it constantly contains a column of tobacco from the lower end of which the tobacco is withdrawn continuously by a toothed roller which feeds it over the said conveyor. The above described known cigarette-making machines are normally fed, in part, with recycled tobacco, withdrawn downstream of the said ascending output chimney by means of shaver devices and frequently introduced directly into the said input chamber. Because of the reduced dimensions of fragments of recycled tobacco, and because of the consequent difficulty with which these are taken up by the carding unit, such a solution does not always guarantee sufficient uniformity of the level of tobacco within the descending chimney. This non-uniformity involves significant disadvantages in that it is manifested as a non-uniformity in the layer of tobacco formed by the said toothed roller on the said conveyor, and therefore as a non-uniformity in the distribution of tobacco along a continuous rod of cigarette which, as is known, is formed at the output of the said ascending chimney.
For the purpose of eliminating this disadvantage, it is known to provide within the descending chimney a plurality of level indicators distributed across the width of the chimney itself and operable to detect the height of the said column at several points. The signals emitted by these level indicators are used to correct the distribution of the tobacco taken up by the carding unit. One known correction method lies in separating the carding unit into a plurality of sub units disposed alongside one another across the width of the descending chimney, and in selectively regulating their feed speed in response to signals received from the said level indicators.
From what has been described above it will be clear that the above described known correction methods involve, in their performance, extremely complicated mechanical devices which, as well as making the associated cigarette-making machines extremely expensive, drastically reduces the reliability of these.